Speaking on a visit to North Wales he said the consequence for such a ban could be closure which would see the loss of hundreds of civilian jobs.

The claim follows the support of Plaid Parliamentary leader Elfyn Llwyd for a petition calling for the banning of low flying over Gwynedd.

Anglesey MP Albert Owen said this highlighted the risk if Plaid have any say in the running of the country under a coalition.

But Plaid’s candidate for Anglesey, Dylan Rees said the low flying ban was not part of the party’s manifesto and he himself did not support the petition.

Mr Ainsworth, who was visiting Broughton, said: “RAF Valley has a bright future as long as we can continue low flying training.

“The consequences of ending low flying training over Snowdonia would be the closure of Valley.”

But Mr Rees said: “Elfyn Llwyd was responding to complaints made to him by his constituents. This is not in the Plaid Cymru manifesto. It is not a petition I have signed and I accept some low flying has to be take place.”

Mr Owen said: “Plaid Cymru are against Trident, the euro-fighter and low flying, they would leave us defenceless. These are the two faces of Plaid Cymru, one supporting the jobs the base provides but the other undermining defence.”

The Defence secretary said the Government has made a £635m commitment to RAF Valley by backing it to lead fighter jet training.

But this £635m figure has come under scrutiny with claims it is misleading as the contract to Ascent is for the entire UK Military Flying Training System, which is not solely based at Valley.

But Mr Owen, who used the figure on election leaflets, said: “This is the only figure available and Valley will have the main tranche of that funding. I am comfortable with using this figure.”

Independent candidate Peter Rogers said: “We are so lucky to have RAF Valley on Anglesey and we cannot undermine that. Plaid should not be standing on Anglesey, they oppose everything we need on the island.”

The Daily Post could not get a comment from Conservative or Liberal Democrat candidates on Anglesey.